Process and apparatus for distilling liquids



.may 2, 1935. D. l. ASHWORTH 2,006,430

PROCESS AND APPARATUS FOR DISTILLING LIQUIDS Filed Sept. 8, 1930 f77/wiwi ys.

Patented July 2, 1935 UNITEDI STATES PROCESS AND APPARATUS FOR DISTILLING LIQUIDS l Daniel Irving Ashworth Wappingers Falls, N. Y.,

assignor to The De Laval Separator Company, New York,` N. Y., a corporation of New Jersey Application September 8, 1930, Serial No.v 480,415

16 Claims.

The object of my invention is to provide an improved process and an improved apparatus for y distilling liquids. While the process and apparatus are available for distilling any liquid, they are found to be particularly efficient for the separation of relatively low boiling point liquids from relatively high boiling point residues, as, for example, the' recovery of allI kinds of solvent washing fluids used in dry cleaning of cloths or in the washing of chips from machined parts.

Y 'I'he object of t he invention is to recover practically all the solvent or other liquid free of obiectionable residues and in a convenient and economical way.

The operation of the process is hereinafter described as it is carried'out in the preferred embodiment of the apparatus shown in the drawing. While the process is described as practiced Afor the recovery of a solvent such as specified, little or no change or adaptation of the process or apparatus is required for distilling other liquids.

In the accompanying drawing, Fig. 1 shows, in elevation and section, an apparatus embodying my invention and adapted for carrying out a process embodying my invention. Fig. 2 is a cross section throughthe oat chamber and the chamber containing the inlet valve. a is the inlet pipe for dirty solvent and b a float-operated valve to control the flow to lthe still through the pipe c. d is an economizer or preheater containing a coil e communicating at one end with pipe c and at the other end with a pipe f, the latter pipe'communicating with the vaporizer g. I

The vaporizer comprises an outer shell h and i an inner shell i between which are a helical guide 7' and a helical heating coil 1c. In the center of the vaporizer is a discharge pipe m having at its bottom an enlarged petticoat. Between the pipe m and the inner shell z' is another helical guide o.

Attached to the bottom of the vaporizer is a residue chamber p containing a heating coil q having its inlet connected to the outlet of the coil k and its outlet to a steam trap 1'. In the bottom of vaporizer g is a device y to separate liquid drops from vapor. z, 2 are pipes leading from separator y to nearly the bottom of residue chamber p. III is a valve controlling the draw-off of liquid from the residue chamber.

The upper end of the vapor discharge pipe m is connected to one end of the shell of the econoinizer d, the other end of which is connected to a condenser s. t and u are outlets from the condenser leading through a trap 1J to the condensate I pump w and the dry vacuum pump In operation, steam is admitted to the coil k in the vaporizer and the coil q in the residue chamber and water is admitted to the water tubes of the condenser s, the vacuum pump :c and the solvent pump w are started, and the solvent isv turned into the still.

The solvent passes through the coil e in the economizer, is heated by hot vapor from the still and enters the annular space between the outer shell h and the inner shell z'. The helical guides 1' cause the solvent to flow around in this space in contact with the heating lcoil k, which causes vaporization of part of the solvent. The mixture of solvent and vapor ows over the top of the inner shell i and, directed by the helical guides o, flows at high speed around and downward between the inner shell i and the discharge pipe m. K

During this flow centrifugal force throws the liquid portion against the inner shell i, which, being heated by the coil Ic, causes vaporization of much more of the liquid. The mixture of liquid and vapor escapes past the edge of the -petticoat m. while still under the 4influence of centrifugal force, which causes the liquid portion to follow down the innerv shell i to theseparator' y, from which it flows through pipes z, a to the bottom of the residue chamber. The vaporized portion escapes up the discharge pipe m and through the economizer d, wherein it surrounds the coile and heats the incoming solvent, and then into the condenser s, where it is condensed and cooled by the upward flowing water. Condensate ows through the pipe t and trap o to the condensate4 pump w. Equalizing pipe u connects the trap v with the'vapor space of the condenser so that liquid will be kept in the condenser to the level of the trap and will be cooled by the incoming Water. Equalizing pipe u also provides a passage through which air leaking into the still may escape to the dry vacuum pump, but, because of bubbling through cool condensate in the trap v, any vapors that try to escape with the air will be condensed.

When sufficient liquid collects in the residue chamber p, some of it flows into a chamber I I containing a oat I2, which, through a shaft I3, actuates the valve b and causes the valve to partially close, so that the rate of feed to the still is such that unvaporized liquid will enter the residue chamber only as fast as the coil q can vaporize it, thus maintaining in the residue chamber a uniform :quantity of liquid suillcient to cover the coil. v

The feed is thus automatically controlled to operate the still at full capacity until enough unvaporizable residues, dirt, tar oil, etc., collect in the chamber to cause the valve b to' close completely. When this occurs the still must be shut down, the vacuum broken, the residue drawn off through the valve l and the still started again.

In the practice of the process as above described, the major heating surface is continuously swept by a rapid flow of wet, that is, highly.

supersaturated, vapor, or a mixture of vapor and liquid, thereby keeping such surface free from the objectionable deposits of solid or tarry substance that areV frequently found on the heating surfaces of ordinary stills. 'I'he major portion of the vaporization being effected whilel flowing at high velocity in a helical path inside a circular heated surface, centrifugal force throws the liquid portion of the mixture against such surface while the vapor moves around nearer the center. This accomplishes the triple purpose of largely freeing the vapors from entrainment of small drops of liquid, washing the heating surface, and promoting rapid transfer of heat to the liquid portion.

When the expression"not completely vaporized liquid is used, it will be understood to include not only liquid partially vaporized but also liquid which, though' warmed, has not been converted into vapor.

Having now fully described invention, what I claim and desire to protect by Letters Patent is:

1.,The process of distilling liquids-which comprises fiowing liquid successively around and through two concentric heating zones in the rst of which theliquid is partially vaporized and in the secondA of which not completely vaporized liquid travels by centrifugal force over a surface separating the two zones and heated by cdnduction and radiation of heat from the first zone, separately removing the vapor and the unvaporized liquid and conveying the latter to a pool of such. liquid in a third heating zone and therein effecting vaporization of the remaining vaporizable constituents and removing the vapor therefrom.

2. The process of distilling liquids which comprises flowing the liquid through a heated zone and therein effecting partial vaporization, then fiowing the mixture of liquid and vapor through another heated zone wherein not completely vaporized liquid is owed rapidly over a heated surface and further vaporization is effected, separately removing the vapor and unvaporized liquid from the second heated zone and conveying the latter to a pool of such liquid in a third heated zone and therein effecting vaporization of the remaining vaporizable constituents and removing the vapor therefrom.

3. The process of distilling liquids which comprises effecting partial vaporization of a liquid by flowing it over a heated surface at a rate exceeding the rate of vaporization by such surface and less than the rate of heat absorption without vaporization, conveying the unvaporized liquid to and maintaining it in contact with a heating surface to effect further vaporization, removing vapor from both loci of vaporization, preventing the escape of liquid from the last locus of vaporization and automatically regulating the fiow of liquid into the first named loci of vaporization to maintain in the last named loci of vaporization a substantially constant volume of unvaporized liquid.

4. The process of distilling liquids which comprises inflowing the liquid to a locus of vaporization and therein flowing not completely vaporized liquid at a rapid rate over a heated surface and thereby effecting its partialv vaporization,

separately removing the vapor and unvaporized liquid and conveying the latter to another locus .of vaporization and therein, by regulating the inflow of liquid to the first named locus of vaporization automatically maintaining a substantially constant volume of liquid in contact with a heated surface while continually removing vapor therefrom and preventing escape of liquid therefrom.

5. In a still, the combination of a preheater, an initial vaporizer, a secondary vaporizer and a residual vaporizing chamber adapted to receive and hold a pool of residual liquid, all arranged in series, a heating coil in the residual vaporizing chamber adapted to vaporize residual liquid therein, a conduit through which liquid is fed to the preheater, and a normally open float-controlled Valve in said conduit and operable to maintain a substantially constant level/1 of the pool of liquid in the residual vaporizing chamber.

6. In a still, the combination gf an outer shell and an inner shell arranged to provide communication between the upper ends of the outer and inner vaporizing chambers, a vapor discharge pipe within and communicating with the lower end of the inner chamber, a feed pipe communicating with the outer chamber, and a vaporizer for residual liquid communicating with the inner x,

vaporizing chamber. Y

7. In a still, the combination of an outer shell and an inner shell arranged to provide communication between the upper ends of the outer and inner vaporizing chambers, a vapor discharge pipe Within and communicating with the lower end of the inner vaporizing chamber and the residual vaporizing chamber hereinafter specified, a vapor chamber communicating with said vapor discharge pipe, a liquid feed pipe extending through said vapor chamber and communicating with the outer vaporizing chamber, and a vaporizer for residual liquid communicating with the inner Vaporizing chamber.

8. In a still, the combination of an outer shell and an inner shell providing outer and inner vaporizing chambers communicating at their upper portions, a vapor discharge pipe Within and communicating with the inner chamber, spiral guides in both vaporizing chambers enforcing a spiral flow of partly vaporized liquid through the outer and inner vaporizing chambers respectively, a feed pipe communicating with the lower portion of the outer vaporizing chamber, and a residual liquid vaporizer arranged below said vaporizing chambers and communicating with the inner vaporizing chamber.

9. In a still, the combination of an outer shell and an inner shell providing outer and inner vaporizing chambers communicating at their upper portions, a vapor discharge pipe within and communicating with the inner chamber, spiral guides in both vaporizing chambers enforcing a spiral flow of partly vaporized liquid through the outer and inner vaporizing chambers respectively, a feed pipe communicating with the lower portion of the outer vaporizing chamber, a residual liquid vaporizer arranged below said vaporizing chambers and communicating with the inner vaporizing chamber, and means providing for heat exchange between the outflowing vapors and the liquid fiowing through the feed pipe.

10. In a still, the combination of an outer shell and an inner shell providing outer and irmer vaporizing chambers communicating at their upper portions, a vapor discharge pipe within and communicating with the inner chamber, spiral guides in both vaporizing chambers enforcing a. spiral flow of partly vaporized liquid through the outer and inner vaporizing chambers respectively, afeed pipe communicating with the lower portion of the outer vaporizing chamber, a residual liquid vaporizer arranged below said vaporizing chambers and communicating with the inner vaporizing chamber, and heating coils extending through the spiral passage in the outer chamber and into the residual liquid vaporizer.

11. In a still, the combination of a chamber' comprising heating surfaces adapted Ato effect partial vaporization of a liquid, a chamber adapted to receive residual liquid and comprising heating surfaces adapted to `effect further vaporization, means providing for the overflow of vapors from both chambers, a conduit through which liquid is fed to the first named chamber, a valve in said conduit, a float controlling said valve, and a fluid passage through which unvaporize'd liquid is adapted to flow from the last named chamber and control the positionv of said iioat and the throttling of said'valve in order to limit the feed of the liquid Itoward the first named chamber.

12. In a still, the combination of two vaporizers arranged in series, one comprising an extended heating surface and means insuring a rapid. flow in a spiral course of not completely vaporized liquid thereover, and the other comprising heating surfaces and aY chamber adapted to receive liquid from the first vaporiz'er and hold a pool completely covering the last named heating surfaces, and means for carrying away the vapors formed in both vaporizers.

13. In a still, two vaporizers and a means to feed liquid to the first vaporizer at a rate exceeding its evaporating capacity and cause it to flow over its heating surface at a high velocity to prevent deposit of unvaporizable constituents, means to separately remove vapor and remaining liquid and conduct the latter to a pool in contact with the heating surface in the second vaporizer and means operable by the liquid in the pool to control the feed and keep it equal to the vaporiz ing capacity of all the vaporizers. v

14. The process of distilling which comprises flowing liquid through a heated zone at a rate exceeding the rate of total vaporization in that zone and therein effecting partial vaporization, removing all the unvaporized liquid from that zone to another heated zone, controlling the inflow of liquid to the first zone and thereby automatically maintaining a constant volumed pool of liquid in the second named zone, vaporizing from such pool the remaining vaporizable constituents and removing the vapors from the specified loci of vaporization.

15. The process of distilling which comprises feeding a liquid into and through a plurality of heating zones in series and therein effecting vaporization, preventing escape of liquid during its flow through the heating zones, conducting all unvaporized residue from the next to the last zone into a final heating zone, varying the level of the pool of liquid in the final zone and thereby automatically controlling the feed to the first zone at a rate exceeding the vaporizing capacity of said first zone but not exceeding the vaporizing capacity of all the zones, and removing vapors from all loci of vaporization.

16. The process of distilling which comprises feeding a liquid into a plurality of heating zones in series and therein effecting vaporization, conducting from all the zones any constituents vaporized therein, conducting into each zone except the first all unvaporized residue from the p receding zone, varying the liquid level in the last zone and thereby controlling the feed to the first zone at a rate exceeding the vaporizing capacity of all zones except the last but not exceeding the vaporizing capacity of all the zones.

D. IRVING ASHWORTH. 

